Splint-forming material



MW-95' *Ja/Zzzasa Nov. 10, 1942.

S. P. LOVELL SPLINT-FORMQING MATERIAL Filed A ril 5, 1959 8 ey P. Lovell, Non, Mam, assignor to Eastex Lsshorotcrieo, Inc, Watertown, Mosh, a corrotion oi i i chusetts Application April 3, 1939, Serial No. 265,673

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invention relates to splints, shorco and the iihn used in the trmtment oi sprains and frocturee.

in treohng oproins end fractures it is the usual practice to form as cast, splint or the like about the site of the injury so as to render obile the injured hone, muscles, etc, odjocent thereto, the usual technique consisting aoentioliy in the application of the so-colled plaster of Paris (dehydrated calcium sulphate) bondage in con junction with slabs of wood, metal braces or the like reinforcing elements; Although this practice has been in vogue for years, ithos several disadvantages which have men recognized by the medical p mfwsion an .2 .w the patient. For 8K- omple, the weight of the plaster cost frequently causes the bones to t in mcledjusted relation end, due to the opacity oi the plaster of Paris,

the use oi Rcentoenroy photogrophy to detw; defective setting is rendered practically imposoilole.

Moreover in splints oi the non-tubular type it is invariobiy' necmscry to employ reinforcing strips of o noture which do not readily conform n M such reinforcing strips tend to soon the gaps Oi' reentmnt portions of irregular surfaces to which they are ognlied, they do not ofioi'd adequate curt and hence it is usually necessary to apply additional plaster, thus greatly increasing the built end weight of the cwt.

The principal objects of the present invention ore to overcome the oioromentioned objectiono and to provide o material which may be reodily formed into on accurately fitting cost or splint icy the direct ocotion of the conditioned motovzhich of applied is in moldablo condition which he inherently capable of setting or heard at tomnemtures endurohlo by the humoo body so no to vide a rigid structure which is oi relatively light weight and permeable to X}- wo. 1

Uther objects oithe invention are to provide e strong and rigid spiint iog motor-lei entirely conformable to the oreo treated and ho on imxnob A time not exg five minutes after application to the treated area, and to provide a splint-dorm mcterlai which after hard ening in situ. may be overlaid end/or incorporated into a, solvent-mitened typo oi t moteriot or alternatively in o plaster of Paris type of cost.

Fr objects and odvontoyeo will he amoroout from a consideration of the folio scription and the accompanying drawing wherein Fig. 1 is a chart illustrating the characteristics of s'. thermoplastic composition useful in the present invention Fig. 2 is a fragmentary perspective view illustrating one type of splint-forming material; and

Fig. 3 is a View similar to Fig. 1, but illustrattrig another type of splint-forming material.

I have observed that when thermoplastic resinolds, which are normally hard at ordinary temperotures, are heated to their flow point and subsequently cooled to temperatures at which they again become hard, the temperature at which they regain their hardness on cooling is not the some as the temperature at winch they lose their initial hardness on heating. in other .words, such compositions possess a hysteresis characteristic which varies with the pcrticulcr resinoid or mixture of resinoids.

I have found that it is possible to modify the hysteresis cha acteristic of normolly hard thermopla-stio resinoido and the like compositions so that upon heating they retain their hardness up to o certain prescribed point or range, after which they become soft and readily moldoble, and upon cooling they retain their moldebility down to e certoin prescribed point or range, after which they become relatively hard and resistont to now. The point or range at which the resin oid heoomeg soft and moldable on heating is herein reien'ed to a the primary softening int,

and the point of range at which the recinoid on cooiing loses its softness moldability is re-;

towed to herein as the secondary suite point," the difference between the two being I index of the hysteresis characteristic.

Although 1' cm not prepared to explain the cc of the hysteresis phenomenon, it is quite hie, if not probable, that such thermoplootio compositions possess to a. greater or lesser extent the character of eupercooled melts in which the constituents function to reduce the crystallizotioo. velocity. However, I do not Wish to limit myself to this exnlonotion.

In accorce with the present invention, I provide a solinhiorming material which is prefembly in sheet form, comprising a fibrous base impre with o water-insoluble or waterresictant thermoplastic composition which 15 normolly hard and resistant to how, having an initial soi o point obove the maximum temperatures enduroblc by the human body, and a second softpoint at or below the maximum temperatureo endux'olole by the human body, thereby perability.

mitting the material, when in moldable condition, to be applied to the site of a fracture or injury to provide on sccurotely fitting splint of light weight and permeable to X-rays.

Thefibrous base may consist of one or more lsyers or plies of s bibuious fabric such as felt, wedding, batting etc., a woven fabric such as osneburg, scrim, terry cloth, etc.; snap fabric such as flannel; or a knitted fabric, all or which are capable of holding an adequate amount of a thermoplastic impregnant to form a. unified splint-forming material of the desired strength and rigidity. In order to insure adequate extensiblllty I preferably employ a laminated inbric base having a cross-grained fabric construction, such as one or more inner layers oi rela-- tively coarse fabric interposed between one or more outer layers of knitted fabric, the wales and courses of the contiguous layers of the outer plies preferably extending in different directions.

The thermoplastic impregnant may comprise natural or synthetic water-insoluble resins which may be modified by or blended with plasticizers or any other ingredients capable of producing a composition having the characteristics indicated in Fig. 1, wherein the line AB represents the maxi mum temperature endurable by the human body (approximately 120 E), the line CD represent-V ing the minimum hardness capable of eflecting substantial immobilization and the line EF rcpresenting minimum soitness permitting mold- The intersection (0:) o! the lines AB and EF represents the minimum softness and maximum temperature at which the thermoplastic composition is moldshle and yet capable of being applied to a patient without injury to thetissue. The curve 0G represents the hardness, softness factor or characteristic when being heated, and the curve OH represents the hardness/soitness factor or characteristic of the same composition when being cooled from s temperature at or above its melting point (ring and ball) It will be observed that the curve 0G intersects the line CD beyond the line AB, and hence at temperatures endurable by the human body the I thermoplastic composition possesses sufllclent rigidity or hardness to insure substantial immobilizstion. The intersection of the curve 06 and 5 the line EB indicates the temperature at which the composition becomes sufficiently soft to permit molding, it being observed that the temperature indicated by the latter point is greater than the maximum temperature endurable by the human body. The curve OH represents the hardness characteristic of the composition when being cooled, and it will be noted that due to hysteresis the curve OH intersects the line AB at a.

point (1/) which is above the line EF, thus showing that at the maximum temperature endurable by the human body the composition is readily moldsble and retains its moldability down to a, temperature indicated by the point z, the intersection of curve OH and line EF, which is considerably lower than the maximum temperature thereof which may be modified by or blended with other materials capable of importing the desired characteristics, or such synthetic resincids M the modifiers and plasticizers.

essences cumaron-indene resins, the cellulose esters, vinyl resins or the i e polymers, or mixtures oi nutu-= ml and mthetic resinoids, with or without on i, In any case, the re sulting. composition should be normally herd sufliciently resistant to flow at temperatures on" durable by the human body so that a splint mode therefrom furnishes substantial immcbllizsticn of the part at which it is applied. and in addition its secondary softening point should be to permit application of the splint without don ger or injuring the patient.

' Where, as is preferred, the fibrous base prises a plurality of plies, the number end weight of such plies, as well as the proportion of thermoplastic impregnant may be untied. throughout a. wide range, depending upon the required strength and rigidity oi the splint to thereirom and such other factors as the inherent strength of the impregnating composition, characteristics 0! the individual plies, etc. he s general rule a satisfactory spllubiorming moterial may be made from a fabric base and a waterinsoluble thermoplastic composition of the ches acter above specified when the proportion of these constituents falls within the following Referring. to Fig. 2, the particular splint-form mg material there shown comprises o, relotively coarse central ply I o! woven fabric such as burlap having a weight oi! approidmstely l on per 50" yard, and on each side or the control ply are intermediste plies 2 and outer plies of knitted fabric preferably having a weight oi proximately 2 oz. per square yard. The poles of the intermediate plies may extend longitudy and the courses transversely and the several plies may be secured together by suitable stitching 5, thus producing a laminated fibrous loose having a. cross-grain construction which permits gree -r extensibility than would otherwise be possible,

In Fig. 8 I have shown a modified form or isleric base which comprises s central ply i oi relatively coarse woven material, intermediate plies 2* of bias cut woven-fabric 0t finer wenve then the central ply I, and outer plies 3 oi material, the several plies being unitcd by e, row of stitching 5.

The laminated fibrous base prc ss shove set forth may be immersed or run through a molten bath of thermoplastic material of the character above described and impregnated to the extent previously indicated, alter which it may be cut up into suitable sizes and shapes for convenient application. A specific exemple of what is now considered a preferred thermoplastic composition for splints adapted for general e is as follows: I

Parts by weight Carnaubs wax -L cc Candelllla wax -n so Ground vulcanized rubber 3d The three ingredients are thoroughly mixed,

. the rubber preferably being added to the molten ilbroua base may be in the molten bath preferably at a temperature of the order of 300 1''. After sumcient impregnation has taken place.

the fibrous base is withdrawn and passed through suitable calenders, thereby'to integrate orunify the impregnated base. Upon cooling, the resulting product becomes hard and rigid and is of light weight and uniform thickness; Due'to the temperature employed in the impregnating treatment the splint-forming material is sterile and without further treatment may be maintained in condition for immediate use since the thermoplastic composition employed does not favor the growth of pathogenic org A splint-forming material comprising a fibrous 'base having the construction illustrated in Fig. 2 and impregnated with the specific thermoplastic composition above set forth possesses the following characteristics:

Weight of central ply oz. per sq. yd I 5.4 Weight of outer plies 2 and 3 1 oz. per sq. yd 2.0 Total weight of fibrous base oz. per sq. yd 7.4 Weight of thermoplastic composition oz. per sq. yd 56.0 Gros weight of splint-forming material oz. per sq. yd 63.4 Thickness of splint-forming material (approximate) inch 0.115

Primary softening point (approximate) -F 130 Secondary softening point (approximate) F 110 In applying the splint made in accordance with the present invention it merely necessary to subject it to a temperature sumcient thoroughly to soften the thermoplastic material so that it becomes readily moldable and to this end the splint-forming material may be placed above a radiator or in an oven heated to a temperature of the order of 150 F. -When thoroughly softened the material may be cooled to a temperature endurable by the patient and directly applied to the site of the injury or fracture which, of course, may be wrapped in a stockinette or the like protective covering. After application it takes but a short time, less than five minutes, before the splint cools to a point at whichthe thermoplastic composition substantially regains its original hardness and rigidity or becomes sumciently rigid to immobilize the part to which it is applied.

I claim:

Splint-forming material comprising a fibrous base impregnated with a, normally hard thermoplastic composition comprising approximately six parts carnauba wax, three parts candelilla wax and one part vulcanized rubber, said composition being sufliciently resistant to flow and deformation at temperaturesendurable by the human body to eil'ect substantial immobilization of the part to which the material is applied, said composition having a primary softening point greater than the maximum temperature endurable by the human body and a secondary softening point r 

